DAMASCUS: Fierce fighting between regime troops and armed rebels rocked parts of Damascus overnight while a Baath party official became the latest victim of a spate of political killings, a watchdog said on Sunday.

The Syrian Observatory for Human Rights also reported that anti-regime demonstrations broke out in several Syrian flashpoints, as leaders of the G8 nations called for a "political transition" to end the relentless violence.

On Saturday, a suicide bomber detonated a car bomb in Deir Ezzor, eastern Syria's biggest city, killing nine people and adding urgency to the G8 calls for all sides to adhere to a UN-brokered truce.

The Syrian Observatory said fighting erupted during the night in the Kafr Sousa district of south Damascus but said there were no immediate reports of casualties.

The Local Coordination Committees, an anti-regime network of activists on the ground in Syria, said Kafr Sousa saw the "arrival of huge reinforcements" of regime troops in the wake of the fighting.

Clashes also broke out in other parts of southern Damascus, the Britain-based Observatory said, adding that gunfire had during the night echoed across the city centre.

"Gunfire was heard in Abbasiyyin Square, and Baghdad and Thawra streets," said the watchdog, referring to high-security areas of the city.

Also overnight, regime forces shelled the outskirts of Douma, a bastion of anti-government sentiment located just north of Damascus, the Observatory said.

It added that, on Sunday, a civilian died of gunshots fired by regime troops in the village of Hasraya in Homs province, a hotbed in central Syria of opposition to President Bashar al-Assad's regime.

And a defector was ambushed and killed by regime forces in Basra al-Sham city of Daraa province in the south.

In Jisr al-Shughur of northwestern Idlib province near the Turkish border, unknown gunmen assassinated a Baath party official, the monitor said, adding there had been a marked increase in political assassinations in past weeks.

"We can confirm that Adib Habb al-Rumman, the village head of the Baath party branch, was definitely assassinated," Observatory head Rami Abdel Rahman told AFP, adding the official worked as a teacher.

"He was targeted on his plot of farmland," said Abdel Rahman.

"There is definitely an increase in assassinations targeting people associated with the regime, be they officials or pro-regime businessmen," the Observatory head said.

Earlier Sunday, two pan-Arab channels reported that six senior regime figures had been assassinated, but two of those named went on national television to prove they were still very much alive.

Hassan Turkmani, assistant to the vice president, and Interior Minister Mohammad al-Shaar slammed the two channels, Doha-based Al-Jazeera and Saudi-owned Al-Arabiya for carrying reports of their alleged deaths, and said all six named in the reports were alive.

"What the disgusting Al-Jazeera is broadcasting is completely false," Shaar told Syrian television by telephone. "We are used to this kind of news, and to these campaigns of lies and slander."

Turkmani in an on-screen interview said the information relayed by Al-Jazeera was "packed with misinformation."

The Observatory, meanwhile, reported demonstrations breaking out on Sunday in several areas of Idlib and in Hama, a restive central province, calling for the ouster of the regime.

In Daraa province, demonstrations were also held calling for the release of activist and citizen journalist Mohammed al-Hariri, who according to Reporters Without Borders was sentenced to death for "high treason."

Hariri was arrested on April 16, RSF said, after he gave an interview to Al-Jazeera from his home in Daraa province.

More than 12,000 people, the majority of them civilians, have died in Syria since an anti-regime revolt broke out in March last year, according to the Observatory.

The G8 -- which includes long-time Syrian-ally Russia -- called on Saturday for a "Syrian-led, inclusive political transition leading to a democratic, plural political system."

The group, huddled at Camp David, outside Washington, also called on the Syrian government and all parties to "immediately and fully adhere" to an internationally-backed plan to end violence.

"The Syrian government and all parties must immediately and fully adhere to commitments to implement the six-point plan of UN and Arab League Joint Special Envoy... Kofi Annan," a joint statement said.